Ammonit Wind Tunnel: Uncertainty by 0,05 m/s to 0,083 m/s on wind speed calibrations

We are proud to announce that starting for calibrations performed after 01.12.2021, we have now thanks to the implementation of a LDA (Laser Doppler Anemometer) a reduced uncertainty on the wind speed calibrations performed by Ammonit Wind Tunnel.
Our Dakks accreditation states now ≤ 0,05 m/s uncertainty for the wind speed.

Reference measurement with Pitot tube and LDA

A calibration of a wind sensor consists in the comparison of the measurement output of the calibrated sensor with the measurement output of the reference measurement equipment of the Wind Tunnel.

According to the IEC 61400-12-1 ed.2 (2017) standard, this comparison is realised for all wind speeds between 4 and 16 m/s.

One of the most important components in the chain of uncertainties of this calibration is the uncertainty of the reference measurement equipment of the Wind Tunnel.

Up to 2018 the reference measurement equipment of the Wind Tunnel for measuring the wind velocity was based on Pitot tubes.

Since 2019 we have introduced on the top of the measurement with Pitot tube a further reference measurement with LDA (Laser Doppler Anemometer).

Reduction of the uncertainty

Thanks to this double reference measurement (Pitot tubes and LDA), we were able to reduce significantly the overall uncertainty of the calibration process,

from 0,10 m/s till 2021

to 0,05 to 0,06 m/s
for calibration between 01.12.2021 and 27.08.2023

and 0,05 m/s to 0,083 m/s

for calibrations performed after 28.08.2023.

Our process has been audited and accredited by Dakks (the German calibration accreditation body), see last page of accreditation D-K-20511-01-00:
AWT Download

Remarks:

1.    0,05 m/s is the lowest possible accredited uncertainty. Due to our calibration process it is not possible in all constellations (type of sensor, wind speed etc.) to achieve this low uncertainty. In some constellations the uncertainty is slightly higher.
2.    The reduced uncertainty is valid only for wind velocity (speed) calibration. There is no reduction of the wind direction uncertainty, which is still 0,8°.

Where do I see this reduced uncertainty on my calibration certificate?

The reduced uncertainty values can be seen in the table with the measurement results.

Example for Thies/Risoe Windsensor/Vector Windspeed cup anemometer: The table is on the beginning of the page 3 and the uncertainty “unc. m/s” is on the last column of the table.

The uncertainty is between 0,05 m/s and 0,083 m/s.